Method for patterning a coating on a surface and device including a patterned coating

This application is a continuation of U.S. patent application Ser. No. 17/313,836, filed May 6, 2021, which is a continuation of U.S. patent application Ser. No. 16/279,930 filed Feb. 19, 2019, which application is a continuation of U.S. patent application Ser. No. 15/527,702, filed May 17, 2017, which is a National Stage Entry of International Application No. PCT/IB2016/056442, filed Oct. 26, 2016, which claims the benefit of and priority to U.S. Provisional Application No. 62/246,597, filed Oct. 26, 2015, U.S. Provisional Application No. 62/277,989, filed Jan. 13, 2016, U.S. Provisional Application No. 62/373,927, filed Aug. 11, 2016, and U.S. Provisional Application No. 62/377,429, filed Aug. 19, 2016, the contents of all such applications being incorporated herein by reference in their entireties.

The following generally relates to a method for depositing an electrically conductive material on a surface. Specifically, the method relates to selective deposition of the electrically conductive material on a surface for forming an electrically conductive structure of a device.

Organic light emitting diodes (OLEDs) typically include several layers of organic materials interposed between conductive thin film electrodes, with at least one of the organic layers being an electroluminescent layer. When a voltage is applied to electrodes, holes and electrons are injected from an anode and a cathode, respectively. The holes and electrons injected by the electrodes migrate through the organic layers to reach the electroluminescent layer. When a hole and an electron are in close proximity, they are attracted to each other due to a Coulomb force. The hole and electron may then combine to form a bound state referred to as an exciton. An exciton may decay through a radiative recombination process, in which a photon is released. Alternatively, an exciton may decay through a non-radiative recombination process, in which no photon is released. It is noted that, as used herein, internal quantum efficiency (IQE) will be understood to be a proportion of all electron-hole pairs generated in a device which decay through a radiative recombination process.

A radiative recombination process can occur as a fluorescence or phosphorescence process, depending on a spin state of an electron-hole pair (namely, an exciton). Specifically, the exciton formed by the electron-hole pair may be characterized as having a singlet or triplet spin state. Generally, radiative decay of a singlet exciton results in fluorescence, whereas radiative decay of a triplet exciton results in phosphorescence.

More recently, other light emission mechanisms for OLEDs have been proposed and investigated, including thermally activated delayed fluorescence (TADF). Briefly, TADF emission occurs through a conversion of triplet excitons into singlet excitons via a reverse inter system crossing process with the aid of thermal energy, followed by radiative decay of the singlet excitons.

An external quantum efficiency (EQE) of an OLED device may refer to a ratio of charge carriers provided to the OLED device relative to a number of photons emitted by the device. For example, an EQE of 100% indicates that one photon is emitted for each electron that is injected into the device. As will be appreciated, an EQE of a device is generally substantially lower than an IQE of the device. The difference between the EQE and the IQE can generally be attributed to a number of factors such as absorption and reflection of light caused by various components of the device.

An OLED device can typically be classified as being either a “bottom-emission” or “top-emission” device, depending on a relative direction in which light is emitted from the device. In a bottom-emission device, light generated as a result of a radiative recombination process is emitted in a direction towards a base substrate of the device, whereas, in a top-emission device, light is emitted in a direction away from the base substrate. Accordingly, an electrode that is proximal to the base substrate is generally made to be light transmissive (e.g., substantially transparent or semi-transparent) in a bottom-emission device, whereas, in a top-emission device, an electrode that is distal to the base substrate is generally made to be light transmissive in order to reduce attenuation of light. Depending on the specific device structure, either an anode or a cathode may act as a transmissive electrode in top-emission and bottom-emission devices.

An OLED device also may be a double-sided emission device, which is configured to emit light in both directions relative to a base substrate. For example, a double-sided emission device may include a transmissive anode and a transmissive cathode, such that light from each pixel is emitted in both directions. In another example, a double-sided emission display device may include a first set of pixels configured to emit light in one direction, and a second set of pixels configured to emit light in the other direction, such that a single electrode from each pixel is transmissive.

In addition to the above device configurations, a transparent or semi-transparent OLED device also can be implemented, in which the device includes a transparent portion which allows external light to be transmitted through the device. For example, in a transparent OLED display device, a transparent portion may be provided in a non-emissive region between each neighboring pixels. In another example, a transparent OLED lighting panel may be formed by providing a plurality of transparent regions between emissive regions of the panel. Transparent or semi-transparent OLED devices may be bottom-emission, top-emission, or double-sided emission devices.

While either a cathode or an anode can be selected as a transmissive electrode, a typical top-emission device includes a light transmissive cathode. Materials which are typically used to form the transmissive cathode include transparent conducting oxides (TCOs), such as indium tin oxide (ITO) and zinc oxide (ZnO), as well as thin films, such as those formed by depositing a thin layer of silver (Ag), aluminum (Al), or various metallic alloys such as magnesium silver (Mg:Ag) alloy and ytterbium silver (Yb:Ag) alloy with compositions ranging from about 1:9 to about 9:1 by volume. A multi-layered cathode including two or more layers of TCOs and/or thin metal films also can be used.

Particularly in the case of thin films, a relatively thin layer thickness of up to about a few tens of nanometers contributes to enhanced transparency and favorable optical properties (e.g., reduced microcavity effects) for use in OLEDs. However, a reduction in the thickness of a transmissive electrode is accompanied by an increase in its sheet resistance. An electrode with a high sheet resistance is generally undesirable for use in OLEDs, since it creates a large current-resistance (IR) drop when a device is in use, which is detrimental to the performance and efficiency of OLEDs. The IR drop can be compensated to some extent by increasing a power supply level; however, when the power supply level is increased for one pixel, voltages supplied to other components are also increased to maintain proper operation of the device, and thus is unfavorable.

In order to reduce power supply specifications for top-emission OLED devices, solutions have been proposed to form busbar structures or auxiliary electrodes on the devices. For example, such an auxiliary electrode may be formed by depositing a conductive coating in electrical communication with a transmissive electrode of an OLED device. Such an auxiliary electrode may allow current to be carried more effectively to various regions of the device by lowering a sheet resistance and an associated IR drop of the transmissive electrode.

Since an auxiliary electrode is typically provided on top of an OLED stack including an anode, one or more organic layers, and a cathode, patterning of the auxiliary electrode is traditionally achieved using a shadow mask with mask apertures through which a conductive coating is selectively deposited, for example by a physical vapor deposition (PVD) process. However, since masks are typically metal masks, they have a tendency to warp during a high-temperature deposition process, thereby distorting mask apertures and a resulting deposition pattern. Furthermore, a mask is typically degraded through successive depositions, as a conductive coating adheres to the mask and obfuscates features of the mask. Consequently, such a mask should either be cleaned using time-consuming and expensive processes or should be disposed once the mask is deemed to be ineffective at producing the desired pattern, thereby rendering such process highly costly and complex. Accordingly, a shadow mask process may not be commercially feasible for mass production of OLED devices. Moreover, an aspect ratio of features which can be produced using the shadow mask process is typically constrained due to shadowing effects and a mechanical (e.g., tensile) strength of the metal mask, since large metal masks are typically stretched during a shadow mask deposition process.

Another challenge of patterning a conductive coating onto a surface through a shadow mask is that certain, but not all, patterns can be achieved using a single mask. As each portion of the mask is physically supported, not all patterns are possible in a single processing stage. For example, where a pattern specifies an isolated feature, a single mask processing stage typically cannot be used to achieve the desired pattern. In addition, masks which are used to produce repeating structures (e.g., busbar structures or auxiliary electrodes) spread across an entire device surface include a large number of perforations or apertures formed on the masks. However, forming a large number of apertures on a mask can compromise the structural integrity of the mask, thus leading to significant warping or deformation of the mask during processing, which can distort a pattern of deposited structures.

According to some embodiments, a device (e.g., an opto-electronic device) includes: (1) a first electrode; (2) an organic layer disposed over the first electrode; (3) a nucleation promoting coating disposed over the organic layer; (4) a nucleation inhibiting coating covering a first region of the opto-electronic device; and (5) a conductive coating covering a second region of the opto-electronic device.

According to some embodiments, a device (e.g., an opto-electronic device) includes: (1) a substrate; (2) a nucleation inhibiting coating covering a first region of the substrate; and (3) a conductive coating including a first portion and a second portion. The first portion of the conductive coating covers a second region of the substrate, the second portion of the conductive coating partially overlaps the nucleation inhibiting coating, and the second portion of the conductive coating is spaced from the nucleation inhibiting coating by a gap.

According to some embodiments, a device (e.g., an opto-electronic device) includes: (1) a substrate including a first region and a second region; and (2) a conductive coating including a first portion and a second portion. The first portion of the conductive coating covers the second region of the substrate, the second portion of the conductive coating overlaps a portion of the first region of the substrate, and the second portion of the conductive coating is spaced from the first region of the substrate by a gap.

According to some embodiments, a device (e.g., an opto-electronic device) includes: (1) a substrate; (2) a nucleation inhibiting coating covering a first region of the substrate; and (3) a conductive coating covering a laterally adjacent, second region of the substrate. The conductive coating includes magnesium, and the nucleation inhibiting coating is characterized as having an initial sticking probability for magnesium of no greater than about 0.02.

According to some embodiments, a manufacturing method of a device (e.g., an opto-electronic device) includes: (1) providing a substrate and a nucleation inhibiting coating covering a first region of the substrate; and (2) depositing a conductive coating covering a second region of the substrate. The conductive coating includes magnesium, and the nucleation inhibiting coating is characterized as having an initial sticking probability for magnesium of no greater than 0.02.

It will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous components. In addition, numerous specific details are set forth in order to provide a thorough understanding of example embodiments described herein. However, it will be understood by those of ordinary skill in the art that the example embodiments described herein may be practiced without some of those specific details. In other instances, certain methods, procedures and components have not been described in detail so as not to obscure the example embodiments described herein.

In one aspect according to some embodiments, a method for depositing an electrically conductive coating on a surface is provided. In some embodiments, the method is performed in the context of a manufacturing method of an opto-electronic device. In some embodiments, the method is performed in the context of a manufacturing method of another device. In some embodiments, the method includes depositing a nucleation inhibiting coating on a first region of a substrate to produce a patterned substrate. The patterned substrate includes the first region covered by the nucleation inhibiting coating, and a second region of the substrate that is exposed from, or is substantially free of or is substantially uncovered by, the nucleation inhibiting coating. The method also includes treating the patterned substrate to deposit the conductive coating on the second region of the substrate. In some embodiments, a material of the conductive coating includes magnesium. In some embodiments, treating the patterned substrate includes treating both the nucleation inhibiting coating and the second region of the substrate to deposit the conductive coating on the second region of the substrate, while the nucleation inhibiting coating remains exposed from, or is substantially free of or is substantially uncovered by, the conductive coating. In some embodiments, treating the patterned substrate includes performing evaporation or sublimation of a source material used to form the conductive coating, and exposing both the nucleation inhibiting coating and the second region of the substrate to the evaporated source material.

As used herein, the term “nucleation inhibiting” is used to refer to a coating or a layer of a material having a surface which exhibits a relatively low affinity towards deposition of an electrically conductive material, such that the deposition of the conductive material on the surface is inhibited, while the term “nucleation promoting” is used to refer to a coating or a layer of a material having a surface which exhibits a relatively high affinity towards deposition of an electrically conductive material, such that the deposition of the conductive material on the surface is facilitated. One measure of nucleation inhibiting or nucleation promoting property of a surface is an initial sticking probability of the surface for an electrically conductive material, such as magnesium. For example, a nucleation inhibiting coating with respect to magnesium can refer to a coating having a surface which exhibits a relatively low initial sticking probability for magnesium vapor, such that deposition of magnesium on the surface is inhibited, while a nucleation promoting coating with respect to magnesium can refer to a coating having a surface which exhibits a relatively high initial sticking probability for magnesium vapor, such that deposition of magnesium on the surface is facilitated. As used herein, the terms “sticking probability” and “sticking coefficient” may be used interchangeably. Another measure of nucleation inhibiting or nucleation promoting property of a surface is an initial deposition rate of an electrically conductive material, such as magnesium, on the surface relative to an initial deposition rate of the conductive material on another (reference) surface, where both surfaces are subjected or exposed to an evaporation flux of the conductive material.

As used herein, the terms “evaporation” and “sublimation” are interchangeably used to generally refer to deposition processes in which a source material is converted into a vapor (e.g., by heating) to be deposited onto a target surface in, for example, a solid state.

As used herein, a surface (or a certain area of the surface) which is “substantially free of” or “is substantially uncovered by” a material refers to a substantial absence of the material on the surface (or the certain area of the surface). Specifically regarding an electrically conductive coating, one measure of an amount of an electrically conductive material on a surface is a light transmittance, since electrically conductive materials, such as metals including magnesium, attenuate and/or absorb light. Accordingly, a surface can be deemed to be substantially free of an electrically conductive material if the light transmittance is greater than 90%, greater than 92%, greater than 95%, or greater than 98% in the visible portion of the electromagnetic spectrum. Another measure of an amount of a material on a surface is a percentage coverage of the surface by the material, such as where the surface can be deemed to be substantially free of the material if the percentage coverage by the material is no greater than 10%, no greater than 8%, no greater than 5%, no greater than 3%, or no greater than 1%. Surface coverage can be assessed using imaging techniques, such as using transmission electron microscopy, atomic force microscopy, or scanning electron microscopy.

is a schematic diagram illustrating a process of depositing a nucleation inhibiting coatingonto a surfaceof a substrateaccording to one embodiment. In the embodiment of, a sourceincluding a source material is heated under vacuum to evaporate or sublime the source material. The source material includes or substantially consists of a material used to form the nucleation inhibiting coating. The evaporated source material then travels in a direction indicated by arrowtowards the substrate. A shadow maskhaving an aperture or slitis disposed in the path of the evaporated source material such that a portion of a flux travelling through the apertureis selectively incident on a region of the surfaceof the substrate, thereby forming the nucleation inhibiting coatingthereon.

illustrate a micro-contact transfer printing process for depositing a nucleation inhibiting coating on a surface of a substrate in one embodiment. Similarly to a shadow mask process, the micro-contact printing process may be used to selectively deposit the nucleation inhibiting coating on a region of a substrate surface.

illustrates a first stage of the micro-contact transfer printing process, wherein a stampincluding a protrusionis provided with a nucleation inhibiting coatingon a surface of the protrusion. As will be understood by persons skilled in the art, the nucleation inhibiting coatingmay be deposited on the surface of the protrusionusing various suitable processes.

As illustrated in, the stampis then brought into proximity of a substrate, such that the nucleation inhibiting coatingdeposited on the surface of the protrusionis in contact with a surfaceof the substrate. Upon the nucleation inhibiting coatingcontacting the surface, the nucleation inhibiting coatingadheres to the surfaceof the substrate.

As such, when the stampis moved away from the substrateas illustrated in, the nucleation inhibiting coatingis effectively transferred onto the surfaceof the substrate.

Once a nucleation inhibiting coating has been deposited on a region of a surface of a substrate, a conductive coating may be deposited on remaining uncovered region(s) of the surface where the nucleation inhibiting coating is not present. Turning to, a conductive coating sourceis illustrated as directing an evaporated conductive material towards a surfaceof a substrate. As illustrated in, the conducting coating sourcemay direct the evaporated conductive material such that it is incident on both covered or treated areas (namely, region(s) of the surfacewith the nucleation inhibiting coatingdeposited thereon) and uncovered or untreated areas of the surface. However, since a surface of the nucleation inhibiting coatingexhibits a relatively low initial sticking coefficient compared to that of the uncovered surfaceof the substrate, a conductive coatingselectively deposits onto the areas of the surfacewhere the nucleation inhibiting coatingis not present. For example, an initial deposition rate of the evaporated conductive material on the uncovered areas of the surfacemay be at least or greater than about 80 times, at least or greater than about 100 times, at least or greater than about 200 times, at least or greater than about 500 times, at least or greater than about 700 times, at least or greater than about 1000 times, at least or greater than about 1500 times, at least or greater than about 1700 times, or at least or greater than about 2000 times an initial deposition rate of the evaporated conductive material on the surface of the nucleation inhibiting coating. The conductive coatingmay include, for example, pure or substantially pure magnesium.

It will be appreciated that although shadow mask patterning and micro-contact transfer printing processes have been illustrated and described above, other processes may be used for selectively patterning a substrate by depositing a nucleation inhibiting material. Various additive and subtractive processes of patterning a surface may be used to selectively deposit a nucleation inhibiting coating. Examples of such processes include, but are not limited to, photolithography, printing (including ink or vapor jet printing and reel-to-reel printing), organic vapor phase deposition (OVPD), and laser induced thermal imaging (LITI) patterning, and combinations thereof.

In some applications, it may be desirable to deposit a conductive coating having specific material properties onto a substrate surface on which the conductive coating cannot be readily deposited. For example, pure or substantially pure magnesium typically cannot be readily deposited onto an organic surface due to low sticking coefficients of magnesium on various organic surfaces. Accordingly, in some embodiments, the substrate surface is further treated by depositing a nucleation promoting coating thereon prior to depositing the conductive coating, such as one including magnesium.

Based on findings and experimental observations, it is postulated that fullerenes and other nucleation promoting materials, as will be explained further herein, act as nucleation sites for the deposition of a conductive coating including magnesium. For example, in cases where magnesium is deposited using an evaporation process on a fullerene treated surface, the fullerene molecules act as nucleation sites that promote formation of stable nuclei for magnesium deposition. Less than a monolayer of fullerene or other nucleation promoting material may be provided on the treated surface to act as nucleation sites for deposition of magnesium in some cases. As will be understood, treating the surface by depositing several monolayers of a nucleation promoting material may result in a higher number of nucleation sites, and thus a higher initial sticking probability.

It will also be appreciated that an amount of fullerene or other material deposited on a surface may be more, or less, than one monolayer. For example, the surface may be treated by depositing 0.1 monolayer, 1 monolayer, 10 monolayers, or more of a nucleation promoting material or a nucleation inhibiting material. As used herein, depositing 1 monolayer of a material refers to an amount of the material to cover a desired area of a surface with a single layer of constituent molecules or atoms of the material. Similarly, as used herein, depositing 0.1 monolayer of a material refers to an amount of the material to cover 10% of a desired area of a surface with a single layer of constituent molecules or atoms of the material. Due to, for example, possible stacking or clustering of molecules or atoms, an actual thickness of a deposited material may be non-uniform. For example, depositing 1 monolayer of a material may result in some regions of a surface being uncovered by the material, while other regions of the surface may have multiple atomic or molecular layers deposited thereon.

As used herein, the term “fullerene” refers to a material including carbon molecules. Examples of fullerene molecules include carbon cage molecules including a three-dimensional skeleton that includes multiple carbon atoms, which form a closed shell, and which can be spherical or semi-spherical in shape. A fullerene molecule can be designated as C, where n is an integer corresponding to a number of carbon atoms included in a carbon skeleton of the fullerene molecule. Examples of fullerene molecules include C, where n is in the range of 50 to 250, such as C, C, C, C, C, C, C, C, and C. Additional examples of fullerene molecules include carbon molecules in a tube or cylindrical shape, such as single-walled carbon nanotubes and multi-walled carbon nanotubes.

illustrates an embodiment of a device in which a nucleation promoting coatingis deposited prior to the deposition of a conductive coating. As illustrated in, the nucleation promoting coatingis deposited over regions of the substratethat are uncovered by a nucleation inhibiting coating. Accordingly, when the conductive coatingis deposited, the conductive coatingforms preferentially over the nucleation promoting coating. For example, an initial deposition rate of a material of the conductive coatingon a surface of the nucleation promoting coatingmay be at least or greater than about 80 times, at least or greater than about 100 times, at least or greater than about 200 times, at least or greater than about 500 times, at least or greater than about 700 times, at least or greater than about 1000 times, at least or greater than about 1500 times, at least or greater than about 1700 times, or at least or greater than about 2000 times an initial deposition rate of the material on a surface of the nucleation inhibiting coating. In general, the nucleation promoting coatingmay be deposited on the substrateprior to, or following, the deposition of the nucleation inhibiting coating. Various processes for selectively depositing a material on a surface may be used to deposit the nucleation promoting coatingincluding, but not limited to, evaporation (including thermal evaporation and electron beam evaporation), photolithography, printing (including ink or vapor jet printing, reel-to-reel printing, and micro-contact transfer printing), OVPD, LITI patterning, and combinations thereof.

illustrate a process for depositing a conductive coating onto a surface of a substrate in one embodiment.

In, a surfaceof a substrateis treated by depositing a nucleation inhibiting coatingthereon. Specifically, in the illustrated embodiment, deposition is achieved by evaporating a source material inside a source, and directing the evaporated source material towards the surfaceto be deposited thereon. The general direction in which the evaporated flux is directed towards the surfaceis indicated by arrow. As illustrated, deposition of the nucleation inhibiting coatingmay be performed using an open mask or without a mask, such that the nucleation inhibiting coatingsubstantially covers the entire surfaceto produce a treated surface. Alternatively, the nucleation inhibiting coatingmay be selectively deposited onto a region of the surfaceusing, for example, a selective deposition technique described above.

While the nucleation inhibiting coatingis illustrated as being deposited by evaporation, it will be appreciated that other deposition and surface coating techniques may be used, including but not limited to spin coating, dip coating, printing, spray coating, OVPD, LITI patterning, physical vapor deposition (PVD) (including sputtering), chemical vapor deposition (CVD), and combinations thereof.

In, a shadow maskis used to selectively deposit a nucleation promoting coatingon the treated surface. As illustrated, an evaporated source material travelling from the sourceis directed towards the substratethrough the mask. The mask includes an aperture or slitsuch that a portion of the evaporated source material incident on the maskis prevented from traveling past the mask, and another portion of the evaporated source material directed through the apertureof the maskselectively deposits onto the treated surfaceto form the nucleation promoting coating. Accordingly, a patterned surfaceis produced upon completing the deposition of the nucleation promoting coating.

illustrates a stage of depositing a conductive coatingonto the patterned surface. The conductive coatingmay include, for example, pure or substantially pure magnesium. As will be explained further below, a material of the conductive coatingexhibits a relatively low initial sticking coefficient with respect to the nucleation inhibiting coatingand a relatively high initial sticking coefficient with respect to the nucleation promoting coating. Accordingly, the deposition may be performed using an open mask or without a mask to selectively deposit the conductive coatingonto regions of the substratewhere the nucleation promoting coatingis present. As illustrated in, an evaporated material of the conductive coatingthat is incident on a surface of the nucleation inhibiting coatingmay be largely or substantially prevented from being deposited onto the nucleation inhibiting coating.

illustrate a process for depositing a conductive coating onto a surface of a substrate in another embodiment.

In, a nucleation promoting coatingis deposited on a surfaceof a substrate. For example, the nucleation promoting coatingmay be deposited by thermal evaporation using an open mask or without a mask. Alternatively, other deposition and surface coating techniques may be used, including but not limited to spin coating, dip coating, printing, spray coating, OVPD, LITI patterning, PVD (including sputtering), CVD, and combinations thereof.

In, a nucleation inhibiting coatingis selectively deposited over a region of the nucleation promoting coatingusing a shadow mask. Accordingly, a patterned surface is produced upon completing the deposition of the nucleation inhibiting coating. Then in, a conductive coatingis deposited onto the patterned surface using an open mask or a mask-free deposition process, such that the conductive coatingis formed over exposed regions of the nucleation promoting coating.

In the foregoing embodiments, it will be appreciated that the conductive coatingformed by the processes may be used as an electrode or a conductive structure for an electronic device. For example, the conductive coatingmay be an anode or a cathode of an organic opto-electronic device, such as an OLED device or an organic photovoltaic (OPV) device. In addition, the conductive coatingmay also be used as an electrode for opto-electronic devices including quantum dots as an active layer material. For example, such a device may include an active layer disposed between a pair of electrodes with the active layer including quantum dots. The device may be, for example, an electroluminescent quantum dot display device in which light is emitted from the quantum dot active layer as a result of current provided by the electrodes. The conductive coatingmay also be a busbar or an auxiliary electrode for any of the foregoing devices.

Accordingly, it will be appreciated that the substrateonto which various coatings are deposited may include one or more additional organic and/or inorganic layers not specifically illustrated or described in the foregoing embodiments. For example, in the case of an OLED device, the substratemay include one or more electrodes (e.g., an anode and/or a cathode), charge injection and/or transport layers, and an electroluminescent layer. The substratemay further include one or more transistors and other electronic components such as resistors and capacitors, which are included in an active-matrix or a passive-matrix OLED device. For example, the substratemay include one or more top-gate thin-film transistors (TFTs), one or more bottom-gate TFTs, and/or other TFT structures. A TFT may be an n-type TFT or a p-type TFT. Examples of TFT structures include those including amorphous silicon (a-Si), indium gallium zinc oxide (IGZO), and low-temperature polycrystalline silicon (LTPS).

The substratemay also include a base substrate for supporting the above-identified additional organic and/or inorganic layers. For example, the base substrate may be a flexible or rigid substrate. The base substrate may include, for example, silicon, glass, metal, polymer (e.g., polyimide), sapphire, or other materials suitable for use as the base substrate.

The surfaceof the substratemay be an organic surface or an inorganic surface. For example, if the conductive coatingis for use as a cathode of an OLED device, the surfacemay be a top surface of a stack of organic layers (e.g., a surface of an electron injection layer). In another example, if the conductive coatingis for use as an auxiliary electrode of a top-emission OLED device, the surfacemay be a top surface of an electrode (e.g., a common cathode). Alternatively, such an auxiliary electrode may be formed directly beneath a transmissive electrode on top of a stack of organic layers.

illustrates an electroluminescent (EL) deviceaccording to one embodiment. The EL devicemay be, for example, an OLED device or an electroluminescent quantum dot device. In one embodiment, the deviceis an OLED device including a base substrate, an anode, organic layers, and a cathode. In the illustrated embodiment, the organic layersinclude a hole injection layer, a hole transport layer, an electroluminescent layer, an electron transport layer, and an electron injection layer.

The hole injection layermay be formed using a hole injection material which generally facilitates the injection of holes by the anode. The hole transport layermay be formed using a hole transport material, which is generally a material that exhibits high hole mobility.